Do Sri Lankan long-distance trains have toilets?

Yes, all Sri Lankan long-distance trains do have toilets on board, mostly at the ends of each carriage. Still, the cleanliness and the overall condition can really shift depending on which class you are travelling in, because things are not always the same.

In the first-class carriages, and also in the newer air-conditioned ones, you will usually find Western-style toilets with running water, maintained pretty well. Second-class and third-class carriages often rely on simpler squat toilets, so it is strongly recommended to bring your own toilet paper, hand sanitiser, and wet wipes.